Could this possibly be the symptoms of the coil going bad, or maybe the compressor (attached to the distributor) or maybe the points. (As I have no sure way of measuring the functionability of these parts from lack of tools, I would rather try replacing parts first.) I'm certainly no mechanic, but I'm sure I can figure out the problem through replacement.
The only thing in that area that I haven't changed since I bought the car is the coil, so I guess I'll start with that.
1976 230.4 W115